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Control Statements

Control Statements:-Control statements are used to manage flow of execution.
Statements are:-
1.     If statement
2.     If-else
3.     Switch-case
4.     Break
5.     Continue
6.     Return
If Statement:-if statement is used for control statement or statements, those statements we want to control we have to write inside if block those statements will execute only when the condition is true.
Syntax:-
Single statement
Multiple statement
If(condition)                                     
Statement1;
If(condition) 
{                                    
Statement1;
Statement2;
}
If(condition)
{                                    
Statement1;
}


Example1:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
if(true)
System.out.println("inside if");
System.out.println("outside if");
}
}
Output:-
C:\JAVATECH>javac TestIF.java
C:\JAVATECH>java TestIF
inside if
outside if
Example2:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
if(false)
System.out.println("inside if");
System.out.println("outside if");
}
}
Output:-
C:\JAVATECH>javac TestIF.java
C:\JAVATECH>java TestIF
outside if
Example3:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
if(true){
System.out.println("inside if statement1");
System.out.println("inside if statement2");
System.out.println("inside if statement3");
}
System.out.println("outside if statement1");
System.out.println("outside if statement2");
}
}
output:-
C:\JAVATECH>javac TestIF.java
C:\JAVATECH>java TestIF
inside if statement1
inside if statement2
inside if statement3
outside if statement1
outside if statement2
Example4:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
if(false){
System.out.println("inside if statement1");
System.out.println("inside if statement2");
System.out.println("inside if statement3");
}
System.out.println("outside if statement1");
System.out.println("outside if statement2");
}
}
output:-
C:\JAVATECH>javac TestIF.java
C:\JAVATECH>java TestIF
outside if statement1
outside if statement2

If-Else Statement:-if-else statement having two blocks one is if block or true block and another is else or false block but at a time only one block will execute if the given condition is true then if block will execute if condition is false then false block will execute
Syntax:-
Single statement
Multiple statement
If(condition)                                     
Statement1;
else
Statement2;
If(condition) 
{                                   
Statement1;
Statement2;
}
else
{
Statement3;
Statement4;
      }
If(condition)
{                                     
Statement1;
}
else
{
Statement2;
      }


Example5:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
if(true){
System.out.println("Condition is true");
System.out.println("Inside if statement1");
System.out.println("Inside if statement2");
}
else
{
System.out.println("Condition is false");
System.out.println("Inside else statement1");
System.out.println("Inside else statement2");
}
}
}
Output:-
C:\JAVATECH>javac TestIF.java
C:\JAVATECH>java TestIF
Condition is true
Inside if statement1
Inside if statement2

Example6:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
if(false){
System.out.println("Condition is true");
System.out.println("Inside if statement1");
System.out.println("Inside if statement2");

}
else
{
System.out.println("Condition is false");
System.out.println("Inside else statement1");
System.out.println("Inside else statement2");
}
}
}
Output:-
C:\JAVATECH>javac TestIF.java
C:\JAVATECH>java TestIF
Condition is false
Inside else statement1
Inside else statement2

Switch-Case:-if we want to use multiple options then we have to use switch-case statements. In switch case statements case can be in any order. If expression is match in any case then execution will start and remaining all cases will execute without checking of any other case. If we want to execute only particular case then we have to use break statement in each case and break statement must be last statement in any case. When break statement executed then control will transfer to out of switch statement.


Syntax:-
switch(expression)
{
case 1:statement1;
case 2: statement2;
case 3:statement3;
case 4: statement4;
default: default statement;
}
switch(expression)
{
case 1:{statement1;}
case 2: {statement2;}
case 3:{statement3;}
case 4: statement4;
default: default statement;
}

Example1:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
int n=1;
switch(n)
{
case 1:
System.out.println("This is case 1");
case 2:
System.out.println("This is case 2");
case 3:
System.out.println("This is case 3");
default:
System.out.println("This is Default case");
}
}
}
Output:-
C:\JAVATECH>javac TestIF.java
C:\JAVATECH>java TestIF
This is case 1
This is case 2
This is case 3
This is Default case
Example2:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
int n=3;
switch(n)
{
case 1:
System.out.println("This is case 1");
case 2:
System.out.println("This is case 2");
case 3:
System.out.println("This is case 3");
default:
System.out.println("This is Default case");
}
}
}
Output:-
C:\JAVATECH>javac TestIF.java
C:\JAVATECH>java TestIF
This is case 3
This is Default case
Example3:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
int n=5;
switch(n)
{
case 1:
System.out.println("This is case 1");
case 2:
System.out.println("This is case 2");
case 3:
System.out.println("This is case 3");
default:
System.out.println("This is Default case");
}
}
}
Output:-
C:\JAVATECH>javac TestIF.java
C:\JAVATECH>java TestIF
This is Default case
Example4:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
int n=2;
switch(n)
{
case 1:
System.out.println("This is case 1");
break;
case 2:
System.out.println("This is case 2");
break;
case 3:
System.out.println("This is case 3");
break;
default:
System.out.println("This is Default case");
}}}
Output:-
C:\JAVATECH>javac TestIF.java
C:\JAVATECH>java TestIF
This is  case 2

Example5:-TestIF.java
class TestIF
{
public static void main(String[]args)
{
int n=2;
switch(n)
{
case 1:
System.out.println("This is case 1");
break;
System.out.println("This is  also case 1");
case 2:
System.out.println("This is case 2");
break;
case 3:
System.out.println("This is case 3");
break;
default:
System.out.println("This is Default case");
}}}
Output:-
C:\JAVATECH>javac TestIF.java
TestIF.java:11: error: unreachable statement
System.out.println("This is  also case 1");
^

1 error
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